Mixed-phase generator and use thereof

ABSTRACT

The present disclosure provides a method of producing a mixed-phase environment. A plurality of supercooled liquid particles are dispersed into a fluid to form a first stream. A plurality of ice particles are dispersed into a fluid to form a second stream. The first and second streams are mixed to form a third stream. The present disclosure also provides a system for producing a mixed-phase environment. The system includes an ice generator, an ice disperser, a water disperser, a first fluid source coupled to the water dispenser, a second fluid source fluidly coupled to the ice disperser, a first flow chamber fluidly coupled to the first fluid source and having an outlet, a second flow chamber fluidly coupled to the second fluid source and having an outlet, and a third flow chamber that includes an inlet fluidly coupled to the outlets of the first and second flow chambers.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of, and incorporates by reference, U.S. Provisional Patent Application No. 61/472,043, filed Apr. 5, 2011.

FIELD

The present disclosure relates, generally, to a method and a system for producing a mixed-phase environment. In a specific example, the method and system can be used to produce a mixed-phase of ice particles and water droplets, such as to simulate a mixed-phase cloud.

BACKGROUND

Mixed-phase clouds include both supercooled water and ice particles. Mixed-phase clouds have been implicated in various atmospheric processes, including lightning formation. Charge separation may result from ice particles colliding with growing particles of graupel. Such charge separation may be a precursor to the development of lightening.

Mixed-phase clouds also have been implicated in the performance of aircraft. For example, mixed-phase clouds may increase ice accretion on aircraft surfaces, thus potentially influencing aircraft performance or stability. Mixed-phase particles also may affect the operation of aircraft components, such as when ice or other particles are injected into an aircraft engine. For example, in some aircraft, such as turbopropeller aircraft, ingestion of particles into the engine can lead to power loss. For jet engines, particle injection can reduce engine efficiency, particularly at higher altitudes or lower temperatures. In addition to effects from the particles in the mixed-phase cloud, other mixed-phase cloud properties, such as lightening production and turbulence, can also influence aircraft performance and safety. In mid-level commuter aircraft flights, at least one serious incident every two years may be attributable to the effects of mixed-phase clouds.

Originally, investigations into atmospheric phenomena were studied by physical simulation. However, the facilities used for such studies typically suffered from various drawbacks. For example, each facility was typically rather large and expensive. Furthermore, each facility was typically constructed to investigate a particular phenomenon, and was not easily adapted to other uses, or even more refined studies. Moreover, at least some in the art felt that physical simulators were not capable of adequately reproducing the complexity of atmospheric phenomena.

Accordingly, much recent work to elucidate atmospheric phenomena and replicate or simulate its effects has focused on theoretical studies. However, the complexity and uncertainty in atmospheric studies can also make theoretical studies of limited use. For example, information from theoretical studies may not, in at least some cases, correlate well with real world conditions.

SUMMARY

The present disclosure provides a system and a method for producing a mixed-phase environment. In one embodiment of the disclosed method, a plurality of particles of a first phase, such as supercooled liquid particles, are dispersed in a fluid to form a first stream. A plurality of particles of a second phase, such as ice particles, are dispersed in a fluid to form a second stream. The first and second streams are mixed to produce a third stream. A least a portion of the third stream is a mixed-phase of the particles of the first and second phases, such as a mixture of ice particles and supercooled liquid particles.

In a particular configuration, the first and second streams converge in near parallel flows to form the third stream. In further configurations, at least a portion of the third stream includes a portion where the first and second streams flow proximate each other in an at least substantially laminar manner, such as the confluence of two rivers having near parallel flows throughout the depth. The volume of the first and second streams, in some examples, is at least substantially the same at the point of mixing. In some examples, the properties of the third stream, such as its turbulence, composition, or flow rate, are altered using a fourth stream, such as injecting air into the third stream to create more turbulence in the third stream. In another example, the turbulence is adjusted through the use of flow obstacles, such as by using rods, particularly adjustable rods, located or positionable normal to the flow of the stream. In a more specific example, the rods protrude into the flow for a distance sufficient to introduce a desired amount of turbulence into the stream, such as a distance between about 0.1 mm and about 50 mm or between about 0.5 mm and about 5 mm. According to another implementation, turbulence in the third stream is influenced by using different flow rates for the first and second streams.

In a specific implementation, the method includes generating ice particles having a controlled distribution of crystal habits, such particles being at least substantially monodisperse in a particular crystal habit. According to a more specific example, the method includes determining the distribution of crystal habits in an environment of interest and generating particles having at least substantially the same distribution as in the environment of interest. In a particular configuration, ice particles having a controlled distribution of crystal habits are grown in a fall chamber.

In some implementations where the particles of the first phase are supercooled water particles and the particles of the second phase are ice particles, the third stream includes a region consisting essentially of ice particles, a region consisting essentially of supercooled water particles, and a region that includes a mixed-phase of ice particles and supercooled water particles. In a more specific implementation, the third stream includes a region consisting essentially of a mixed-phase of ice particles and supercooled water particles. The distribution of the first, second, and third regions is, in some examples, controlled by altering the properties of the first or second streams, such as their composition or flow properties, such as their flow rate or flow volume.

The method can include measuring a property, such as a property of the third stream. For example, a sensor can be located in the third stream. In some implementations, the sensor is moved in the third stream to place the sensor in a portion of the third stream having a different composition, such as a different proportion of ice particles and supercooled water particles, than the previous sensor location. Some implementations of the method use a controller to move the sensor, such as in response to a detected composition.

The method can include further steps, such as generating water or ice particles and storing the ice or water particles before dispersing them into a fluid. The method can also include one or more conditioning steps, such as conditioning ice particles prior to dispersing them in a fluid. Additives, including cloud condensation nuclei or ice nuclei, can be added in various stages of the method, such as prior to particle generation, during particle generation or conditioning, during particle dispersing, during mixing of the first and second streams, or to the third or fourth streams.

In another aspect, the present disclosure provides a system for producing a mixed-phase environment. The system includes a first particle generator, such as an ice generator, a second particle generator, such as water droplet generator, a first disperser coupled to the first particle generator, and a second disperser coupled to the second particle generator. A first fluid source is fluidly coupled to the first disperser. A second fluid source is fluidly coupled to the second disperser. A first flow chamber is fluidly coupled to the first fluid source and includes an outlet. A second flow chamber is fluidly coupled to the second fluid source and includes an outlet. The system further includes a third flow chamber to which the outlets of the first and second flow chambers are fluidly coupled. The outlets of the first and second flow chambers are positioned such that flows from the outlets flow into the third chamber. Flow into the third chamber is arranged to be parallel or at least substantially parallel. In some examples, the first, second, and third chambers are vertically oriented. In other examples, the chambers are horizontally oriented.

In a particular configuration, the system includes a third fluid source coupled to a fourth flow chamber. The fourth flow chamber has an outlet coupled to the third flow chamber. The outlet of the fourth flow chamber, in a particular example, is disposed intermediate the outlets of the first and second flow chambers. In one implementation, the third fluid source is a source of air.

The system can contain additional components, for example, a sensor for monitoring one or more properties of a fluid or mixed phase of the system. In some configurations the sensor is coupled to an actuator and can be moved within the third chamber. The system, in some configurations, includes a controller, such as to control the sensor or actuator. In another configuration, the system includes an additive source coupled to one or more of the first or second particle generators, the first or second fluid sources, the first or second flow chambers, the third flow chamber, the air source, or the fourth flow chamber.

According to another implementation of the disclosed method, a system as disclosed herein is coupled to an existing flow system, such as a wind tunnel.

There are additional features and advantages of the subject matter described herein. They will become apparent as this specification proceeds.

In this regard, it is to be understood that this is a summary of varying aspects of the subject matter described herein. The various features described in this section and below for various embodiments may be used in combination or separately. Any particular embodiment need not provide all features noted above, nor solve all problems or address all issues in the prior art noted above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a fall tower that can be used to produce ice crystals for use in an embodiment of the system or method of the present disclosure.

FIG. 2 is a schematic diagram of a mixing chamber that can be used in an embodiment of the system or method of the present disclosure.

FIG. 3 is a schematic diagram of mixing chamber that can be used in an alternative embodiment of the system or method of the present disclosure.

FIG. 4 is a schematic diagram of a system according to an embodiment of the present disclosure.

FIG. 5 is a flowchart of an embodiment of the disclosed method for generating a mixed-phase.

FIG. 6 is a schematic diagram of a system according to an embodiment of the present disclosure using a vertically oriented mixing chamber.

DETAILED DESCRIPTION

Unless otherwise explained, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. In case of any such conflict, or a conflict between the present disclosure and any document referred to herein, the present specification, including explanations of terms, will control. The singular terms “a,” “an,” and “the” include plural referents unless context clearly indicates otherwise. Similarly, the word “or” is intended to include “and” unless the context clearly indicates otherwise. The term “comprising” means “including;” hence, “comprising A or B” means including A or B, as well as A and B together. All numerical ranges given herein include all values, including end values (unless specifically excluded) and intermediate ranges.

Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure, suitable methods and materials are described herein. The disclosed materials, methods, and examples are illustrative only and not intended to be limiting.

For example, the following discussion generally describes forming a mixed-phase of supercooled water droplets and ice particles. However, in at least some embodiments, the system and method are not limited to water or to any specific phase of matter. For example, the system and method may be applied to materials other than water or other phases of matter. A particular stream is not limited to containing only one phase of matter. For example, a feed phase of supercooled water may include solid particles. In addition to not being limited to water, or aqueous solutions or particles formed therefrom, the two streams need not be of the same material or compound. The two streams could be of different materials or include mixtures of materials. However, a specific embodiment creates a mixed-phase of supercooled water droplets and ice particles from a feed stream consisting essentially of ice particles and a feed stream consisting essentially of supercooled water droplets. In some embodiments, the flow rates of the two streams are at least approximately equal. In other embodiments, the streams have different flow rates, which may be used to influence the turbulence of the combined stream.

“Additives” refers to inorganic, organic, or biological materials that are added to one or more components of the system or method of the present disclosure in order to tailor the properties of a generated mixed-phase. The additives may be added to the feed streams of the mixed-phase, during creation of one or more phases to be mixed, or directly to the mixed-phase. Additives may be of any phase or combination of phases.

In some examples, additives are used to alter the properties of a component of the mixed-phase. For example, when the mixed-phase includes supercooled water drops, additives may include inorganic compounds, such as salts or minerals, onto which water vapor condenses to form liquid droplets. Similarly, additives may be used as nucleation sources for ice particles, When used to simulate atmospheric phenomena, additives may be added to the method or system to more accurately reproduce the phenomena, such as its chemical composition.

In some examples, suitable additives include cloud condensation nuclei or ice nuclei. Additives can also include organic or inorganic gases, such as carbon dioxide, oxygen, nitrogen, water, halocarbons, carbon monoxide, nitrogen oxides, ammonia, sulfur dioxide, ozone, methane, or mixtures thereof Aerosol particles, which may or may not be cloud condensation particles or ice nuclei, can also be used as an additive. In yet further examples, additives can include other forms of the components used to produce the mixed-phase, such as materials having at least one of a different phase, temperature, pressure, size, or other different chemical or physical property. For example, when a mixed-phase is formed from supercooled water droplets and smaller ice particles, large ice particles, such as hail-sized ice particles, can be included as an additive.

“Cloud condensation nuclei,” sometimes referred to as cloud seeds, are particles around which cloud drops form. For example, cloud condensation nuclei can act as a surface on which water vapor can condense. Examples of materials that can serve as cloud condensation nuclei include combustion products, including soot or carbon black, such as may be produced by combusting paper, wood, or plastics, such as polypropylene. Other cloud condensation nuclei include inorganic materials, such as ammonia gas, sulfur dioxide, minerals, including montmorillonite or kaolinite, clays, salts, such as silicates, sulfates, ammonium salts, or metal halides, such as sodium chloride, silver iodide, or lead iodide, organic particles, biological particles, such as bacteria, or mixtures thereof. Cloud condensation nuclei typically have a diameter of between about 0.01 μm and about 100 μm, such as between about 0.1 μm and about 10 μm. In some examples, cloud condensation nuclei are included in an amount between about 0.001 particles/cc and about 100,000 particles/cc, such as between about 100 particles/cc and about 1,000 particles/cc.

“Habit” refers to the typical appearance of a type of crystal, such as ice crystals. Many materials crystallize iii forms having particular geometric shapes or typical size ranges. Examples of crystal habits include acicular, amygdaloidal, anhedral, bladed, botryoidal, columnar, coxcomb, dendritic, dodecahedral, drusy, enantiomorphic, equant, euhedral, fibrous, filiform, foliated, granular, hemimorphic, mamillary, massive, nodular, octahedral, plumose, prismatic, pseudo-hexagonal, pseudomorphous, radiating, reniform, reticulated, rosette, sphenoid, stalactitic, stellate, striated, subhedral, tabular, and wheat sheaf.

A particular material may be capable of forming crystals in multiple habits. For example, ice forms different crystal habits depending on, among other factors, the moisture content, temperature, type of nucleation, and growth time during crystallization or growth.

“Ice conditioner” refers to a component that is used to change one or more properties of ice particles or a fluid in which the ice particles are dispersed. For example, the conditioner may be used to influence one or more properties of the particles or fluid, such as the concentration, pressure (including reduced pressures, such as pressures lower than atmospheric or ambient pressure), temperature, or vapor mass fraction of the particles. In particular examples, the pressure in the diffusion chamber is between about 5 hPa and about 5000 hPa, such as between about 100 hPa and about 1,000 hPa or between about 150 hPa and about 600 hPa. The temperature in the diffusion chamber, in some examples is between about −150° C. and about 25° C., such as between about −70° C. and about 5° C. In further examples, the degree of water supersaturation in the diffusion chamber is between about 0% and about 200% over ice, such as between about 1% and about 100% or between about 1% and about 25%.

In a specific example, the ice conditioner is a diffusion chamber. For example, selection of appropriate conditions in a diffusion chamber can allow for ice particle growth or modification by processes such as condensation freezing, where liquid water condenses onto ice particles and then freezes, or contact nucleation, where supercooled droplets freeze onto ice particles. In a specific example, the diffusion chamber includes thermally controllable plates, which may be maintained at different temperatures to establish a thermal gradient that can allow convection to be suppressed or produce different types of particles at different points in the gradient. Diffusion chambers can allow previously formed particles to aggregate, grow, melt, or evaporate.

“Ice nuclei” refers to particulate matter that can act as the nuclei for the formation of ice crystals. Ice nuclei can be used to raise the temperature at which ice forms. For example, ice nuclei can increase the temperature at which ice forms in the atmosphere from about −42° C. to about −10° C. Accordingly, in the system and method of the present disclosure, ice nuclei can be used to produce ice particles having desired properties or can be added to sources of a mixed-phase or to the mixed-phase itself. Examples of material that can serve as ice nuclei include, without limitation, inorganic materials, such as salts, including metal halides, such as metal chlorides or iodides, or metal sulfates, including, without limitation, those where the metal is lithium, sodium, potassium, magnesium, calcium, chromium, manganese, molybdemum, iron, cobarlt nickel, copper, zinc, or mixtures thereof, or minerals; organic materials, such as soot; or biological matter, such as bacteria. In some examples, the ice nuclei have an average particle diameter of between about 0.05 μm and about 500 μm, more typically between about 0.1 μm and about 10 μm. In some examples, cloud condensation nuclei are include in an amount between about 0.0001 particles/cc and about 10,000 particles/cc, such as between about 0.001 particles/cc and about 10 particles/cc.

“Ice particle generator” refers to a system or process for producing particles of ice that may be used in the disclosed system or method. In some implementations, ice particle generators produce ice particles in bulk form. For example, although the size range of ice particles may be controlled, at least to some extent, other properties of the particles, such as their crystal habit are not controlled or have greater variability. Examples of such ice particle generators include components that produce ice particles by abrading larger ice sources, such as blocks of ice. Another example of this type of particle generator is a snow gun, which typically atomizes r through a nozzle using cold, compressed air.

In further implementations, ice particle generators may be selected that allow greater control over the properties of the ice particles. In a specific example, the ice particle generator is a fall column. An example of a fall column, generally indicated as 100, is illustrated in FIG. 1. The fall column 100 includes a growth chamber 104 coupled to a lower chamber 108. One or more components of the fall column 100, including the growth chamber 104 and the lower chamber 108, are typically insulated and/or refrigerated.

A nebulizer 112 is fluidly coupled to the growth chamber 104, such as using a length of conduit 116, such as plastic or metal tubing. In a particular example, the nebulizer produces water droplets having a diameter of between about 10 μm and about 20 μm. One suitable nebulizer 112 is the Sunbeam Model 694 (Sunbeam Products, Inc., Boca Raton, Fla.).

A seeder 120 is fluidly coupled to the growth chamber 104. The seeder 20 may be, for example, a spring 124 circulated by a motor 128 between the growth chamber 104 and a coolant 132, such as an insulated container of liquid nitrogen.

A number of instruments may be in communication with the lower chamber 108, such as by being directly coupled to, or indirectly obtaining information from, the lower chamber 108. For example, FIG. 1 illustrates a Fourier transform infrared (FTIR) spectrometer 136 that is able to record spectra of materials passing by a view port 140 in the side of the chamber 108. The lower chamber 108 also includes one or more sensors 144, which may be an imaging device, such as a Cloudscope (described in Rule, M., “Initial Assessment of the DRI Cloudscope,” MRF Technical Note No. 23, (Jan. 19, 1998), incorporated by reference herein to the extent not inconsistent with the present disclosure), a T-probe, a particle counter (such as the Model 278B optical particle counter, available from Met One Instruments, Inc., of Grants Pass, Oreg.), a particle sizer, a scattering detector, an optical power detector, a nephelometer, a beta attenuation monitor, an aethalometer, a photoacoustic instrument, a temperature sensor, a pressure sensor, a water sensor, an ice sensor, a humidity sensor, a rimmed rod, an electricity sensor, such as metal plate or spheres, or combinations thereof. In another specific embodiment, the sensor 144 is a T-probe, as described in Hallett et al., “High resolution measurement of ice—supercooled water cloud interfaces,” Paper #3.3, AMS 12th Conference on Cloud Physics, Madison, Wis. (Jul. 10-14, 2006), incorporated by reference herein to the extent not inconsistent with the present disclosure. In other implementations, the sensor 144 is omitted.

A blackbody 148 is included in the lower chamber 108. The blackbody may be used, for example, to absorb radiation that can interfere with the operation of the sensor 144. A suitable blackbody 148 may formed by placing a brass cone in a brass box, the interior surfaces of which are coated with black paint. The box is filled with a coolant, such as liquid nitrogen, during operation. In some embodiments, the blackbody 148 is omitted.

An outlet 152 connects the lower chamber 108 to external components that can serve to couple the fall tower 100 to other elements of the present disclosure, such as to be mixed with water droplets to form a mixed-phase environment. A valve 156 is positioned between the outlet 152 and the lower chamber 108. In the embodiment illustrated in FIG. 1, the outlet 152 is coupled to particle storage 160. Storage 160 may be, for example, a chamber where a fan 164 circulates the particles until they are transferred to a fluid source 168 for further use. A valve 172 is posited between storage 160 and the fluid source 168.

In some embodiments, the lower chamber 108 includes a fan 176. In other configurations, the fan 176 is omitted or located elsewhere in the fall column 100.

In operation, droplets 180 from the nebulizer 112 travel through the conduit 116 and enter the growth chamber 104. As they pass by the cooled spring 124, the droplets 180 are nucleated to form ice particles 184. Typically, the cold spring 124 allows the droplets 180 to be nucleated homogenously to produce ice particles 184 having desired properties, such as size and habit. The properties of the particles 184 can be further selected using the fan 176, such as to influence the rate at which the particles 184 travel through the growth chamber 104. The residence time in the lower chamber 108 or growth chamber 104 can affect the size or habit of the crystals formed using the fall tower 100.

Once in the lower chamber 108, the particles 184 can be observed instrumentally, such as using the FTIR 136 through the viewing port 140. Background radiation may be reduced through the use of the blackbody 148, located opposite the port 140 in the lower chamber 108. The properties of the particles 184 can be further ascertained using the imaging device 144.

When particles 184 are desired for the fluid source 168, or to replenish the supply in the storage area 160, the valve 156 can be opened, such as using a controller (not shown). Particles 184 then pass through the valve 156, into the outlet 152, and then into the storage area 160.

In the storage area 160, the particles are recirculated, such as using the fan 164, until they are needed. The storage area 160, in some examples, is cooled, which can aid in maintaining the particles 184 in the same form as when the particles 184 entered the lower chamber 108.

When the particles 184 are to be used, such as in the method or system of the present disclosure, the valve 172 can be opened to allow particles to pass into the fluid source 168, where they can be transported for further use.

Of course, those of ordinary skill in the art will realize that various modifications can be made to the fall column 100. For example, various components can be added or omitted. In particular, the storage chamber 160 is omitted in alternative embodiments. In yet further implementations, one or more of the instruments in the lower chamber 108 are omitted, or alternative instruments included. In further examples, the fan 176 is omitted. A source of additives, such as cloud condensation nuclei or ice nuclei, is included in some configurations. After formation, the ice particles are transferred to a conditioning unit, in some examples. If the particles are stored, conditioning may occur before or after storage, or a combination thereof.

The process parameters of the ice generator, such as its temperature, humidity, and duration of particle formation, can affect the nature of the ice crystals produced. For example, at warmer temperatures, such as about −8° C., plate habits may predominate, while at cooler temperatures, such as −16° C., dendritic habits may predominate.

“Mixing chamber” refers to a vessel in which at least two streams are brought together to form a mixed-phase environment. In a particular example of the present disclosure, the streams are brought together in a parallel or an at least substantially parallel manner. Bringing together of the streams in this manner can allow the mixed-phase environment to be more precisely or accurately controlled.

One suitable design for a mixing system 200 is illustrated in FIG. 2. In the mixing system 200, first and second conduits 205, 210 enter a mixing chamber 215. Valves 220, 225 are disposed between the mixing chamber 215 and conduits 205, 210, respectively.

Each conduit 205, 210 intersects the mixing chamber 215 such that flows through the respective conduits 205, 210 enter the mixing chamber 215, at least in some implementations, in an at least substantially parallel manner. In a particular configuration, the diameter of the conduits 205, 210 are approximately equal, such as each being about half the diameter of the mixing chamber 215. In another configuration, the flows from the conduits 205, 210 enter the mixing chamber 215 in a parallel or at least substantially parallel and a laminar or at least substantially laminar manner.

The mixing chamber 215, in some embodiments, includes one or more sensors. For example, as shown in FIG. 2, the mixing chamber 215 includes a sensor 230 affixed to the side of the mixing chamber. The sensor 230 may measure parameters such as flow rate, temperature, electromagnetic absorbance (such using a UV-visible or FTIR spectrometer) moisture content, or phase information (such as the proportion of solid and liquid materials in a flow passing through the mixing chamber 215). In further configurations, the sensor 230 is selected as described above for the sensor 144 (FIG. 1).

For the illustrated embodiment, another sensor 235 is shown located in the interior of the mixing chamber 215. The sensor 235 may be selected to measure, without limitation, the properties listed for the sensor 230. The sensor 230 and the sensor 235 may measure the same properties, different properties, or a combination thereof. In at least some configurations, the sensor 235 is movable within the interior of the mixing chamber 215 using an actuator, such as a multi-axes actuator, including gear-driven systems, such as those useable on optical benches. In further embodiment, the sensor 230 and/or 235 are omitted.

In a particular example, a third conduit 240 is coupled to the mixing chamber 215. In a specific example, the third conduit 240 is coupled to a source of gas 245, such as air. The flow of the gas 245 into the mixing chamber 215 may be controlled using a valve 250. In other examples, the third conduit 240 or gas 245 is omitted.

Various changes, additions, or omissions may be made to the mixing system 200. For example, the mixing system 200 may include a source of additives, such as cloud condensation nuclei or ice particles, that is, in various examples, coupled to the first or second conduits 205, 210, the gas source 245, the third conduit 240, or the mixing chamber 215. In further examples, one or more of the valves 220, 225, 250 are omitted.

In one example of how the mixing system 200 may be operated, a flow of supercooled water droplets 255 is transmitted to the mixing chamber 215 through the valve 220. A flow of ice particles 260 is transmitted to the mixing chamber 215 through the valve 225.

In the mixing chamber 215, the two streams 255, 260 combine to form a portion 265 that includes supercooled water, a portion 270 that is made at least substantially of ice particles, and a mixed-phase portion 275 that is a mixed-phase of ice and supercooled water. Although the crosshatching of the mixed-phase portion 275 is uniform in FIG. 2, depending on the conditions of the mixing system 200, the composition of the mixed-phase portion 275 may vary at different regions. For example, areas of the mixed-phase portion 275 closer to the supercooled water droplets 265 or the ice particles 270 may have a higher concentration of the respective closer material.

The sizes, shapes, and compositions of the regions 265, 270, 275 may be influenced by a number of factors, including the flow rates and composition of the streams 255, 260. When used, these parameters may also be affected by a fluid stream from the third conduit 240. For example, the fluid stream from the third conduit 240 may affect the turbulence in the mixing chamber 215, which can affect the properties of the regions 265, 270, 275.

The sensors 230, 235 can be used to measure the properties of the contents of the mixing chamber 215. In a particular implementation, the sensor 235 can be moved within the mixing chamber 215 to identify regions of varying composition. For example, in FIG. 2, as the sensor 235 is moved from the bottom to the top of mixing chamber 215, the sensor 235 would encounter region 270, which substantially includes ice particles. Continuing upwards, the sensor 235 would then encounter region 275, containing a mixture of ice particles and supercooled water droplets. Typically, the sensor 235 would first encounter a portion of region 275 having a higher concentration of ice particles. Further movement would contact the sensor 235 with a portion having nearly equal amounts of ice and water. Yet further movement would contact the sensor 235 with higher concentrations of supercooled water droplets until the sensor 235 reached the region 265, which substantially includes water droplets. The environment of the sensor 235 can also be changed through axial movement. For example, moving the sensor 235 further from the point of mixing can produce move evenly mixed compositions or more turbulent flows.

In some cases, the system of the present disclosure is added to an existing facility, such as an existing wind tunnel. FIG. 3 presents a mixing chamber 300 that may be used in such situations. The mixing chamber is formed by interposing a bifurcated region 310 into a, typically, unitary conduit 320.

A conduit 330 of the bifurcated region is coupled to a first fluid source 340. The first fluid source may be, for example, a source of supercooled water droplets. A conduit 350 of the bifurcated region 310 is coupled to a second fluid source 360. The second fluid source may be, for example, a source of ice particles. The first and second fluid sources 340, 360, in at least some implementations, enter the conduits from radial openings. The first and second conduits 330, 350 are then brought together into a unitary conduit, as in the mixing chamber 200. The mixing chamber 300 is otherwise as described for the mixing chamber 200.

“Water droplet generator” refers to a system for producing water particles that can be used in the system and method of the present disclosure. When controlled drop sizes are desired, various methods can be used. For example, the Vibrating Orifice Aerosol Generator, Model 3450, available from TSI, Inc., of Shoreview, Minn., can be used to produce monodisperse or substantially monodisperse droplets having a diameter between 1 μm and 200 μm. For polydisperse aerosols, various atomizers, including Models 3076, 3079, 9302, and 9306, are available from TSI, Inc., can be used to produce polydisperse aerosols having an average size between 0.01 μm and 2 μm.

The generated droplets can be cooled to a desired temperature, such as to a temperature below the freezing point of water, that is, supercooled. Other methods of generating supercooled water droplets are known in the art, including forcing water through various nozzles using compressed air. Suitable nozzles include the NASA Standard Mod-1 type nozzles, air-assisted atomizing nozzles. Spray bars can be placed in a fluid stream, with each spray bar housing a number of nozzles. The production of supercooled water droplets in this manner is described in NASA technical report 2003-212395, incorporated by reference herein to the extent not inconsistent with the present disclosure.

In some configurations, the water droplet generator includes a source of additives, such as cloud condensation nuclei or ice nuclei. Additives may also be added to help simulate an environment of interest, such as to reproduce atmospheric conditions, including atmospheric particles or pollutants.

General Description

FIG. 4 illustrates one embodiment of a system 400 according to the present disclosure for forming a mixed-phase environment. The system includes a first particle generator 405, such as a water particle generator, coupled to first particle storage 410. The first particle storage 410 is fluidly coupled to a fluid source 415. The fluid source 415 may be, for example, a stream of air, at a desired temperature, into which the particles from the first particle generator 405 may be dispersed. In some examples, fluid source 415 is a fan, gas drawn by a pump (not shown), or gas from a gas source (not shown), such as a source of compressed gas.

In alternate configurations of the system 400, the first particle storage 410 is omitted. The particles from the first generator 405 may be, for example, dispersed directly into the stream of the fluid source 415 and used in other components of the system 400.

In another configuration, the system 400 includes a source of cloud condensation nuclei 420 coupled to a diffusion chamber 425. The diffusion chamber 425 is coupled to the first particle storage 410 in some examples. In other examples, the diffusion chamber 425 is coupled directly to the fluid source 415.

In further implementations, the system 400 includes a source of additives 430, such as cloud condensation nuclei, ice nuclei, or other inorganic, organic, or biological materials, such as simulated pollutants. The additive source 430 may be coupled to one or more components of the system 400, such as the first particle generator 405, the first particle storage 410, the fluid source 415, the cloud condensation nuclei source 420, or the diffusion chamber 425. Although shown as a single unit, in some examples the additive source 430 includes multiple units. The additives supplied by the additive source 430 to the various components can be the same or different.

The system 400 also includes a second particle source 435, such as an ice particle generator, coupled to a particle conditioner 440, such as an ice particle conditioner. Although particle conditioner 440 is shown as a single unit, in practice, it may include multiple discrete units. The particle conditioner 440 is coupled to a second particle storage unit 445. The second particle storage unit 445 is coupled to a second fluid source 450 that disperses the second particles to be used in the system 400. The fluid source 450 may be of the same general types as the fluid source 415 and may be the same type or a different type than the fluid source 415.

In some examples, one or both of the particle conditioner 440 and the second particle storage 445 are omitted. In one such implementation, particles from the second particle generator 435 are dispersed directly into the fluid source 450. In another implementation, particles from the second particle generator 435 are conditioned in the conditioner 440 and then dispersed in the fluid source 450. In yet another implementation, the second particles are stored without conditioning in storage 445 and then dispersed in the fluid source 450.

In examples where both second particle storage 445 and particle conditioner 440 are included, the conditioner 440 may be included upstream of the storage, as shown. However, in other implementations, the particle conditioner 440 is located downstream of the storage unit 445. When multiple conditioners are used, the conditioners 440 may be located upstream, downstream, or both, of the second particle storage 445.

In another implementation, the system 400 includes a source of cloud condensation nuclei or ice nuclei 455. The source 455 is coupled to a diffusion chamber 460. The diffusion chamber 460 is coupled to the second particle generator 435.

In further implementations, the system 400 includes a source of additives 465, such as cloud condensation nuclei, ice nuclei, or other inorganic, organic, or biological materials, such as simulated pollutants. The additive source 465 may be coupled to one or more components of the system 400, such as the second particle generator 435, the particle conditioner 440, the second particle storage 445, the fluid source 450, the cloud condensation nuclei/ice nuclei source 455, or the diffusion chamber 460. Although shown as a single unit, in some examples the additive source 465 includes multiple units. The additives supplied by the additive source 465 to the various components can be the same or different.

The first and second fluid source 415, 450 are fluidly coupled to a mixing chamber 470. As explained above, in some embodiments, the fluid sources 415, 450 enter the mixing chamber 470 in parallel or near-parallel flows.

The mixing chamber 470, in some configurations, includes one or more objects 475 to be studied, such as a vessel or component thereof.

In some embodiments, the system 400 includes an air source 480 coupled to the mixing chamber 470. Various additives, such as from the additive source 465, can be added to the air source 480 or otherwise added to the mixing chamber 470 along with the first and second particles.

One or more sensors 485 are typically connected to the mixing chamber 470. The sensors 485 may be, for example, one or more of the types of sensors listed for the sensor 144 (FIG. 1) or 230 (FIG. 2). The sensors 485 are coupled to a controller 490. The controller may be, for example a commercially available personal computer, such as a WINDOWS—(Microsoft Corp, Redmond, Wash.) based PC running on a CORE 2 QUAD processor (Intel Corp., Santa Clara, Calif.), or workstation or customized computing device. For example, the controller 490 may be of the type typically used to control the particular sensor 485 with which the controller 490 is used.

In at least some implementations, the controller 490 is coupled to other components of the system 400. For example, the controller 490 may be coupled to the fluid sources 415, 450 or the air source 480. In other configurations, the other components of the system 400 are controlled independently or are connected to a different controller than controller 490.

FIG. 5 presents a flowchart of one embodiment of a method 500 for operating the system of FIG. 4. First particles, such as water droplets, are generated in step 505 using the first particle generator 405. In particular implementations of the method 500, generating the first particles includes passing cloud condensation nuclei or ice nuclei from the source 420 through the diffusion chamber 425. The generated particles are optionally stored in step 510 in the first particle storage 410. In step 515, first particles from storage or from a generator are dispersed in the first fluid source 415, such as in a stream of air created by a fan. In further embodiments of the method 500, additives are added during one or more of steps 505, 510, and 515.

In step 520, second particles, such as ice particles, are generated. Although not shown in FIG. 5, step 520, in some embodiments, includes passing ice nuclei or cloud condensation nuclei, such as from the source 455, through the diffusion chamber 460. In a specific embodiment of the method 500, the ice particles are generated by passing water droplets through a fall column.

Optionally, in step 525, the second particles are conditioned in the conditioner 440, such as in a diffusion chamber. The second particles are optionally stored in step 530 in the second particle storage 445. The second particles, from the generator, conditioner, or storage, are dispersed in the second fluid source 450 in step 535. For example, the particles may be dispersed in an air stream created by a fan.

In alternative implementations of the method 500, steps 525 and 530 are performed in the reverse order. In yet another alternative configuration, the second particles may be conditioned both before and after storage. In further embodiments of the method 500, additives are added during one or more of steps 520, 525, 530, and 535.

The fluids containing the first and second are combined in the mixing chamber 470 in step 540. Optionally, the combined flow can be adjusted, such as using the air source 480, in step 545. Additives, such as cloud condensation nuclei or ice nuclei from the additive source 465, can be added in one or both of steps 540 and 545.

The properties of at least one component of the mixing chamber 470 are detected in step 550. Optionally, in step 555, components of the mixing chamber are passed over an object to be tested 475, such as a vessel or vessel component. If step 555 is carried out, the effects of this exposure are determined in optional step 560.

FIG. 6 illustrates a vertically oriented embodiment 600 of a system for forming a mixed-phase environment. The system 600 includes a housing 606. Optionally, the housing 606 is attached to a support, such as a gantry 610. The housing 606 may be support by other means or can be unsupported, other than through placement on an underlying surface. The housing 606 is typically cooled, such as at a temperature of between about 0° C. and about −40° C. In one example, the housing 606 is cooled using a circulating fluid.

The housing 606 is divided into two sections 614, 616 by a separator 620. The separator 620 extends through a portion of the housing 606. Section 614 provides an ice nucleation/ice crystal growth side for forming ice crystals 624. Section 616 provides a cloud droplet side having unnucleated cloud, water particles 628. A portion of the housing 606 below the separator 620 forms a mixing region 632 and a test region 636.

In the mixing region 636, ice particles 624 and cloud (water) particles 628 mix. In some implementations, the amount of mixing can be controlled, such as using a fluid, as described in conjunction with FIG. 2. Sensors are included in the test region 636 and may be configured as described for the sensors 230, 235 of FIG. 2.

Cloud droplets are introduced into the sections 614, 616 through a suitable source, such as an ultrasonic nebulizer. However, cloud droplets may be provided by another suitable water droplet generator. Section 614 includes a suitable ice generator, such as continuous moving wire coil, cooled at its base by immersion in liquid nitrogen. In another example, two cloud water drop spectra are used. In other embodiments, the ice generator is omitted from section 614 and ice particles are introduced into section 614 through a suitable ice particle generator.

An environmental chamber 640 is included in some embodiments. The environmental chamber 640 may house a fan which can be used to control how quickly the ice crystals 624 and water particles 628 pass through the housing 606.

The vertically oriented system 600 can be useful, for example, when the particles to be studied may have significant fallout, such as due to their size, in a horizontally oriented system. The vertically oriented system 600 can generally be constructed and used as described for horizontally oriented systems, including in the system of FIG. 4 and in the method of FIG. 5.

It is to be understood that the above discussion provides a detailed description of various embodiments. The above descriptions will enable those of ordinary skill in the art to make and use the disclosed embodiments, and to make departures from the particular examples described above to provide embodiments of the methods and apparatuses constructed in accordance with the present disclosure. The embodiments are illustrative, and not intended to limit the scope of the present disclosure. The scope of the present disclosure is rather to be determined by the scope of the claims as issued and equivalents thereto. 

1. A method for producing a mixed-phase environment, comprising: dispersing a plurality of supercooled liquid particles in a fluid to form a first stream; dispersing a plurality of ice particles in a fluid to form a second stream; and mixing the first and second streams to produce a third stream, at least a portion of the third stream comprising a mixed-phase of ice particles and supercooled liquid particles.
 2. The method of claim 1, further comprising generating ice particles having a controlled distribution of crystal habits.
 3. The method of claim 2, wherein the distribution is at least substantially monodisperse.
 4. The method of claim 2, wherein the distribution approximates the distribution of crystal habits of ice particles in an atmospheric mixed-phase cloud.
 5. The method of claim 1, further comprising determining the distribution of crystal habits in an environment of interest and generating ice particles having at least substantially the distribution as in the environment of interest.
 6. The method of claim 2, wherein generating ice particles comprises generating ice particles in a fall chamber.
 7. The method of claim 1, wherein the third stream comprises a first region consisting essentially of ice particles, a second region consisting essentially of supercooled water particles, and third region comprising a mixed-phase region comprising ice particles and supercooled water particles.
 8. The method of claim 7, further comprising altering the distribution of the first, second, and third regions by altering the properties of the first or second streams.
 9. The method of claim 8, wherein altering the distribution comprises altering the composition of the first or second stream.
 10. The method of claim 8, wherein altering the distribution comprises altering flow properties of the first or second stream.
 11. The method of claim 10, wherein altering flow properties of the first or second stream comprises altering the flow rate.
 12. The method of claim 10, wherein altering flow properties of the first or second stream comprises altering the flow volume.
 13. The method of claim 1, further comprising locating a sensor in the third stream to measure a property of the third stream.
 14. The method of claim 13, further comprising moving the sensor in the third stream.
 15. The method of claim 1, wherein the first stream and the second stream converge to form the third stream in near parallel flows.
 16. The method of claim 1, the method of claim 1 further adjusting the properties of the third stream using a fourth stream.
 17. The method of claim 16, wherein adjusting the properties of the third stream using a fourth stream comprises injecting air into the third stream to regulate the level of turbulence in the third stream.
 18. The method of claim 1, further comprising: generating ice particles; and storing ice particles; wherein dispersing ice particles in a fluid to form a first stream comprises dispersing stored ice particles.
 19. The method of claim 1, wherein mixing the first and second streams comprises introducing the first stream parallel to the second stream.
 20. The method of claim 1, wherein the volumes of the first and second streams are approximately equal at a point of mixing. 